Twist off caps or screw cap closure systems for bottles are well-known in the art. Typically these systems comprise a closure frame which has integrally joined to it a sealing means to provide a barrier between the environment and the content of the bottle. Often in particular for fruit juice comprising beverages these bottles are provided under a reduced internal pressure such that the twist off cap is slightly deformed by being pulled into the bottle and upon releasing the seal provides an audible signal indicating an intact temper proof.
FR-A-946 554, EP-A-227 087, BE-A-845 904, U.S. Pat. No. 2 040 798, CH-A-256 811 all disclose closures comprising a closure frame and a sealing means which deforms visibly under vacuum pochaying (?) conditions. However some of the prior art documents disclose reusable closure frames or considers the provision of audible temper proof indications.
The sealing means used in these twist off caps is usually provided by polyvinylchloride material. Polyvinylchloride (herinafter abreviated by PVC) does provide certain benefits to the sealing means e. g. the repeatable ability to undergo deformations to provide proper sealing. However, these advantages are balanced with certain disadvantages which are in particular environmental concerns with PVC. Especially when attempting to recycle the closure system it is necessary to remove paint and PVC from the closure frame prior to recycling the closure frame e.g. by melting it. This removal of the PVC and paint is usually achieved by burning but has become very uneconomical due to ecological concerns about PVC fumes and the resulting precautions for the process.
Also PVC has a high affinity to absorb organic compounds. Therefore twist off cap closures having PVC sealing means cannot be reused for containers comprising materials for human consumption because the sealing means will become contaminated, i.e. loaded with the organic compounds present in the container content. Reuse or recycling of sealing means having such contamination is of course prohibited under many local regulatory laws.
On the other hand it would be desirable to recycle or reuse the closure system since it is usually made to be durable enough to allow reuse or if less durable closure systems are employed (for example having a thin walled closure frame) at least recycling without the negative aspects caused by its multimaterial components is desirable.
Hence there is a need to provide a closure system which can be reused or recycled without the problems associated with known screw cap/sealing means. However since consumers have become used to tamper proof indications the present invention needs to provide such a closure system with tamper proof indication either similar to those currently available or alternative tamper proof indication.